Method for producing nitride semiconductor laser light source and apparatus for producing nitride semiconductor laser light source

ABSTRACT

A method for producing a nitride semiconductor laser light source is provided. The nitride semiconductor laser light source has a nitride semiconductor laser chip, a stem for mounting the laser chip thereon, and a cap for covering the laser chip. The laser chip is encapsulated in a sealed container composed of the stem and the cap. The method for producing this nitride semiconductor laser light source has a cleaning step of cleaning the surface of the laser chip, the stem, or the cap. In the cleaning step, the laser chip, the stem, or the cap is exposed with ozone or an excited oxygen atom, or baked by heat. The method also has, after the cleaning step, a capping step of encapsulating the laser chip in the sealed container composed of the stem and the cap. During the capping step, the cleaned surface of the laser chip, the stem, or the cap is kept clean. This method provides a long-life nitride semiconductor laser light source the light emission intensity of which is not easily reduced after a long period of use.

BACKGROUND OF THE INVENTION

1) Field of the Invention

The present invention relates to a method for producing a nitridesemiconductor laser light source that has a long life, and to anapparatus for producing the nitride semiconductor laser light source.

2) Description of the Related Art

Semiconductor laser light sources with short wavelengths of thenear-ultraviolet and ultraviolet regions are generally produced byencapsulating a nitride semiconductor laser chip in the inner space of acap that allows laser light to transmit therethrough, so that the laserchip is shielded from the ambient atmosphere. There is such a problemthat at the time of production, contaminants intrude into the innerspace of the cap and attach to the facet of the resonator of the laserchip, resulting in deteriorated laser characteristics.

The contaminants mean hydrocarbon compounds and siloxane, oftencontained in the ambient atmosphere or generated in the course ofproduction of the laser light source and diffused in the productionatmosphere. Thus, the contaminants attach to the laser chip and capduring the production of the laser light source, and even if a freshatmosphere is used when encapsulating the laser chip in the cap, thecontaminants cannot be prevented from intruding into the cap to becontained therein.

In some cases, contaminants such as hydrocarbon compounds and siloxaneare originally adhered to the constituent members of the laser lightsource. If the laser light source is produced without any treatment, thecontaminants remain inside the cap.

In addition, heat is generated when driving the laser, and because thisdriving heat causes convection of the contaminants in the encapsulatedatmosphere, many of the contaminants are ionized by exposure to shortwavelength laser light. The ionized contaminants are adsorbedintensively and strongly to the facet of the laser chip causing thefacet of the resonator to deteriorate. This reduces with time the lightemission intensity of the laser light source.

To remove the contaminants floating in the encapsulated atmosphere forthe purpose of preventing the facet of the resonator from deteriorating,a technique is proposed in Japanese Patent Application Publication No.2004-14820 such that as shown in FIG. 4, zeolite adsorbent 48 isprovided in cap 43 of laser light source 47.

This technique will be described using the drawing. As shown in FIG. 4,semiconductor laser light source 47 has nitride semiconductor laser chip45, chip-equipped portion 41 for supporting laser chip 45, stem 40 formounting laser chip 45 thereon, bell-shaped cap 43 having, in a topportion, window portion 44 for laser light to transmit therethrough, andlight detecting element 46. Semiconductor laser light source 47 isformed by encapsulating laser chip 45 in a sealed container that is inturn formed by adhering cap 43 to stem 40. On the lower surface of stem40, electrode lead wires 42 are provided.

However, as a result of a study carried out by the present inventors, ithas been found that even when using the above technique, thecontaminants in the encapsulated atmosphere cannot be sufficientlyremoved by adsorption, and when operated for a long period of time, thefacet of the laser chip deteriorates.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a method forproducing a long-life type nitride semiconductor laser light source thelight emission intensity of which is not easily reduced after a longperiod of use, and to provide an apparatus for producing the nitridesemiconductor laser light source.

(1) In order to accomplish the above and other objects, a method forproducing a nitride semiconductor laser light source according to afirst aspect of the present invention is configured as follows.

A method for producing a nitride semiconductor laser light source isprovided. The nitride semiconductor laser light source comprises anitride semiconductor laser chip, a stem for mounting the laser chipthereon, and a cap for covering the laser chip. The laser chip isencapsulated in a sealed container composed of the stem and the cap. Themethod comprises the steps of: a baking step of cleaning a surface ofthe laser chip, the stem, or the cap, the baking step comprising heatingthe laser chip, the stem, or the cap in a first atmosphere; and acapping step of, after the baking step, encapsulating the laser chip inthe sealed container composed of the stem and the cap, the capping stepbeing carried out in a second atmosphere. The second atmosphere is of akind identical to or different from the first atmosphere.

With this structure, since the laser chip is encapsulated in the sealedcontainer after contaminants have been removed out of the sealedcontainer composed of the stem and cap and off the surface of the laserchip by carrying out the baking step prior to the capping step, theamount of the contaminants incorporated in the sealed container at thetime of production of the laser light source is significantly reduced.Thus, even in the case of a long period of use under high temperature,deterioration does not easily occur on the facet of the resonator of thelaser chip by polymerization or decomposition of the contaminants, andthe deterioration with time of the light emission intensity is reduced.This enables the long-time operation of the nitride semiconductor laserlight source.

The method for producing a nitride semiconductor laser light sourceaccording to the first aspect of the present invention may be such thatthe first atmosphere and the second atmosphere each have a vacuum.

The term vacuum is intended to mean an atmosphere of an atmosphericpressure of 1×133.322 Pa (1 Torr) or lower.

The method for producing a nitride semiconductor laser light sourceaccording to the first aspect of the present invention may be such thatthe first atmosphere comprises only an inert gas; and the secondatmosphere comprises an inert gas of a kind identical to or differentfrom the inert gas of the first atmosphere.

That the atmospheres have a vacuum or an inert gas is preferable in thatthe atmosphere gas does not adversely affect the baking and capping.

The method for producing a nitride semiconductor laser light sourceaccording to the first aspect of the present invention may be such thatthe first atmosphere comprises an inert gas, or an inert gas and oxygengas; and the second atmosphere comprises an inert gas and oxygen gas.

When oxygen gas is added in the second atmosphere, which is anencapsulation gas for use in encapsulating the laser chip in the sealedcontainer composed of the stem and cap, laser chip characteristics suchas electrical characteristics are stabilized when the laser light sourceis operated for a long period of time. The oxygen gas concentration inthe second atmosphere is preferably 100 ppm or higher and 80% or lower,more preferably from 0.1% to 40%, and most preferably from 1% to 18%. Ifthe oxygen gas concentration is too low, the effect of characteristicsstabilization is not sufficiently obtained. If the oxygen gasconcentration is too high, the oxygen gas is feared to adversely affectlaser chip characteristics.

Even if oxygen gas in the above range is contained in the firstatmosphere, which is used in the baking step, the laser light source isnot adversely affected.

The method for producing a nitride semiconductor laser light sourceaccording to the first aspect of the present invention may be such thatthe first atmosphere and the second atmosphere each have dry air with amoisture concentration of 1000 ppm or lower.

Because dry air (ambient atmosphere) with a moisture concentration of1000 ppm or lower is mainly composed of approximately 78% nitrogen gas(inert gas), approximately 21% oxygen gas, and approximately 1% argongas (inert gas), advantageous effects similar to those obtained whenusing the above-described mixture of inert gas and oxygen gas areobtained, and the production cost is reduced compared with the case ofusing an inert gas or a mixture gas of inert gas and oxygen gas.

By making the moisture concentration 1000 ppm or lower, even ifcontaminants are incorporated in the dry air, the deterioration(contamination) of the facet is inhibited and the advantageous effectsof the present invention are obtained.

The method for producing a nitride semiconductor laser light sourceaccording to the first aspect of the present invention may be such thatthe first atmosphere or the second atmosphere comprises nitrogen gas orhelium gas.

With this structure, by using helium gas as a heat radiation mediumtaking advantage of its high heat conductivity, heat damage duringdriving of the nitride semiconductor laser chip is significantlyreduced. On the other hand, because nitrogen gas is cheaper than otherinert gases, the use of nitrogen gas for the inert gas reduces theproduction cost of the laser light source.

The method for producing a nitride semiconductor laser light sourceaccording to the first aspect of the present invention may be such thatthe first atmosphere and the second atmosphere comprise identical kindsof gases.

With this structure, since identical kinds of atmospheres are usedthroughout the production process of the laser light source, workassociated with supply of gas is simplified, and the laser light sourceis produced cheaply compared with the use of a plurality of differentkinds of gases.

The method for producing a nitride semiconductor laser light sourceaccording to the first aspect of the present invention may be such thatthe pressure of the second atmosphere is 760×133.322 Pa or lower.

With this structure, by filling the capping portion with gas at apressure of 760×133.322 Pa (760 Torr) or lower, the pressure inside thesealed container of the completed laser light source is made equal to orlower than the ambient atmosphere pressure to thereby enhance theadhesivity of the cap after sealing.

The method for producing a nitride semiconductor laser light sourceaccording to the first aspect of the present invention may be such thatthe nitride semiconductor laser chip has a light emission wavelength of420 nm or shorter.

When contaminants are incorporated inside the laser light source, thefacet of the resonator of the laser chip tends to deteriorate as thelight emission wavelength of the laser light source becomes shorter.However, with the above structure, while using a laser chip of a veryshort wavelength of 420 nm or shorter, which is a light emissionwavelength in the blue-to-ultraviolet regions, since contaminants arenot easily incorporated inside the sealed container at the time ofproduction of the laser light source, the facet of the resonator of thelaser chip is prevented from deteriorating.

If the treatment temperature is lower than 100° C., organic compoundsand siloxane are not sufficiently decomposed and evaporated, and thusthe surface of each constituent member of the laser light source cannotbe cleaned. On the other hand, if the treatment temperature exceeds 500°C., heat damage occurs on the nitride semiconductor laser chip, and thecap and stem are deformed by heat. In the baking step, therefore, thelaser chip, stem, or cap is preferably heated in the range between 100°C. and 500° C. In the case where the treatment temperature exceeds 350°C., there is a high risk of the solder that joints the constituentmembers being melted by heat and thereby the laser light source beingbroken. When the treatment temperature is set at 200° C. or higher,organic compounds and siloxane are reliably decomposed and evaporated.Thus, more preferably, the heating temperature in the baking step isfrom 200° C. to 350° C.

Although the baking time can be selected arbitrarily from the rangebetween 10 minutes and 24 hours, adjustment needs to be carried outconsidering the trade-off between the treatment temperature and thetreatment time, examples including setting the time at 10 minutes whenthe temperature is 500° C., 30 minutes for a temperature of 350° C., 2hours for a temperature of 200° C., and 24 hours for a temperature of100° C.

(2) An apparatus for producing a nitride semiconductor laser lightsource which realizes the method for producing a nitride semiconductorlaser light source according to the first aspect of the presentinvention is configure as follows.

An apparatus for producing a nitride semiconductor laser light sourcecomprises: a baking furnace for leaning a surface of a nitridesemiconductor laser chip, a stem for mounting the laser chip thereon, ora cap for covering the laser chip, the baking furnace heating the laserchip, the stem, or the cap in a first atmosphere; and a capping portionfor encapsulating in a second atmosphere, the laser chip with a cleanedsurface in a sealed container composed of the stem and the cap each witha cleaned surface. The second atmosphere is of a kind identical to ordifferent from the first atmosphere.

(3) In order to solve the above-described and other problems, a methodfor producing a nitride semiconductor laser light source according to asecond aspect of the present invention is configured as follows.

A method for producing a nitride semiconductor laser light source isprovided. The nitride semiconductor laser light source comprises anitride semiconductor laser chip, a stem for mounting the laser chipthereon, and a cap for covering the laser chip. The laser chip isencapsulated in a sealed container composed of the stem and the cap. Themethod comprises the steps of: an ashing step of cleaning a surface ofthe laser chip, the stem, or the cap, the ashing step comprisingexposing the surface of the laser chip, the stem, or the cap with ozoneor an excited oxygen atom; and a capping step comprising after theashing step, supplying a first gas onto the surface of the laser chip,the stem, and the cap; and encapsulating, in an atmosphere of the firstgas, the laser chip in a sealed container composed of the stem and thecap.

The method for producing a nitride semiconductor laser light sourceaccording to the second aspect of the present invention is configuredapproximately the same as the method for producing a nitridesemiconductor laser light source according to the first aspect exceptthat the cleaning treatment is carried out by, instead of baking withthe use of heat, ashing with the use of exposure of ozone or an excitedoxygen atom.

With this structure, since the laser chip is encapsulated in the sealedcontainer after contaminants have been removed out of the sealedcontainer composed of the stem and cap and off the surface of the laserchip by carrying out the ashing step prior to the capping step, theamount of the contaminants incorporated in the sealed container issignificantly reduced, as in the first aspect of the present invention.Thus, even in the case of a long period of use under high temperature,deterioration does not easily occur on the facet of the resonator of thelaser chip by polymerization or decomposition of the contaminants, andthe deterioration with time of the light emission intensity is reduced.This enables the long-time operation of the nitride semiconductor laserlight source.

The method for producing a nitride semiconductor laser light sourceaccording to the second aspect of the present invention may be such thatthe first gas comprises only an inert gas.

The method for producing a nitride semiconductor laser light sourceaccording to the second aspect of the present invention may be such thatthe first gas comprises an inert gas and oxygen gas.

The method for producing a nitride semiconductor laser light sourceaccording to the second aspect of the present invention may be such thatthe first gas has dry air with a moisture concentration of 1000 ppm orlower.

When an inert gas is used for the first gas, which is an encapsulationgas, the semiconductor laser light source is not adversely affected.

Also, when oxygen gas is added in the first gas, which is anencapsulation gas, as described in relation to the production methodaccording to the first aspect, laser chip characteristics such aselectrical characteristics are stabilized when the laser light source isoperated for a long period of time. A preferable range for the oxygengas concentration is the same as in the production method according tothe first aspect.

Also, the effects of using, as the first gas, dry air with a moistureconcentration of 1000 ppm or lower are the same as in the productionmethod according to the first aspect.

The method for producing a nitride semiconductor laser light sourceaccording to the second aspect of the present invention may be such thatthe nitride semiconductor laser chip has a light emission wavelength of450 nm or shorter.

When contaminants are incorporated inside the laser light source, thefacet of the resonator of the laser chip tends to deteriorate as thelight emission wavelength of the laser light source becomes shorter.However, with the above structure, while using a laser chip of awavelength of 450 nm or shorter, and further, 420 nm or shorter, whichare light emission wavelengths in the blue-to-ultraviolet regions, sincecontaminants are not easily incorporated inside the sealed container atthe time of production of the laser light source, the facet of theresonator of the laser chip is prevented from deteriorating.

The method for producing a nitride semiconductor laser light sourceaccording to the second aspect of the present invention may be such thatthe cleaning treatment in the ashing step comprises oxidizing anddecomposing a contaminant adhered to the surface of the laser chip, thestem, or the cap using the ozone or the excited oxygen atom, therebyremoving the contaminant off the surface of the laser chip, the stem, orthe cap.

Excited oxygen atoms (O (1D)) and ozone have strong oxidizing force, andthus with the above structure in which ozone or an excited oxygen atomis exposed to a contaminant such as siloxane and an organic compoundadhered to each constituent member of the laser light source, thecontaminant is gasified by oxidization and decomposition and scatteredoff the surface of each constituent member into the atmosphere of theashing treatment equipment, thereby cleaning the surface of eachconstituent member.

The ozone can be generated by using a known ozone-gas generating method,and the excited oxygen atom can be generated by irradiating oxygen gasor ozone as with ultraviolet light.

The method for producing a nitride semiconductor laser light sourceaccording to the second aspect of the present invention may be such thatthe excited oxygen atom is generated by irradiating the oxygen gassupplied onto the surface of the laser chip, the stern, or the cap withultraviolet light.

With this structure, radiation of ultraviolet light cuts the moleculecombination of organic contaminants. This promotes the decompositioneffect of the contaminant realized by the strong oxidizing force of theozone and excited oxygen atom.

The method for producing a nitride semiconductor laser light sourceaccording to the second aspect of the present invention may be such thatthe ashing step comprises supplying a second gas containing an inert gasonto the surface of the laser chip, the stem, or the cap.

The inert gas or the second gas may comprise nitrogen gas or helium gas.

The method for producing a nitride semiconductor laser light sourceaccording to the second aspect of the present invention may be such thatthe first gas and the second gas comprise identical kinds of gases.

The operations and effects of the above-described structures are thesame as in the production method according to the first aspect of thepresent invention.

The method for producing a nitride semiconductor laser light sourceaccording to the second aspect of the present invention may furthercomprise, between the ashing step and the capping step, a step ofsupplying only the first gas, the inert gas, or the second gas onto thesurfaces of the laser chip, the stem, and the cap.

With this structure, during the time between the ashing step and thecompletion of the capping step, the laser chip, stem, and cap, which aremain constituent members of the laser light source, are not exposed tothe ambient atmosphere but always kept in a sealed state. Contaminantstherefore do not re-adhere to the cleaned surfaces of the members. Thus,contaminants are reliably prevented from intruding into the sealedcontainer at the time of device production, thereby enabling the furtherlong-time operation of the laser light source.

The method for producing a nitride semiconductor laser light sourceaccording to the second aspect of the present invention may be such thatthe treatment temperature during the ashing step is from 100° C. to 500°C.

With this structure, in addition to an accelerated increase in theoxidization activity of the excited oxygen atom and the like uponincrease in the treatment temperature, by making the treatmenttemperature during the ashing step 100° C. or higher, moisture isevaporated off the surface of each member. Insofar as the treatmenttemperature is 500° C. or lower, the promoting effect of the cleaningtreatment is obtained without heat damage on the nitride semiconductorlaser chip and heat deformation of the cap and stem.

The method for producing a nitride semiconductor laser light sourceaccording to the second aspect of the present invention may be such thatthe treatment temperature during the ashing step is from 200° C. to 350°C.

When the treatment temperature is set at 200° C. or higher, the bakingeffect of decomposing and evaporating organic compounds and siloxane isobtained. On the other hand, when the treatment temperature exceeds 350°C., there is a high risk of the solder that joints the constituentmembers being melted by heat and thereby the laser light source being,broken. It is therefore preferable to make the treatment temperaturefrom 200° C. to 350° C.

The method for producing a nitride semiconductor laser light sourceaccording to the second aspect of the present invention may be such thatthe pressure of the first inert gas is 760×133.322 Pa or higher.

With this structure, by filling the capping portion with the inert gasat a pressure of 760×133.322 Pa (760 Torr) or higher, the pressureinside the sealed container of the completed laser light source is madehigher than the ambient atmosphere pressure. This prevents the ambientatmosphere from flowing into the sealed container, that is, contaminantsare prevented from intruding into the sealed container.

The method for producing a nitride semiconductor laser light sourceaccording to the second aspect of the present invention may be such thatthe laser chip is mounted on the stem being subject to ashing in theashing step.

With this structure, it is not necessary to mount the laser chip on thestem in the capping step. This eliminates the need for carrying out thecapping step, by which the laser chip is encapsulated in the sealedcontainer, in a sealed environment for the purpose of preventingadherence of contaminants. Thus, the process for production of the laserlight source and associated equipment are facilitated.

The method for producing a nitride semiconductor laser light sourceaccording to the second aspect of the present invention may be such thatthe ashing step comprises cleaning surfaces of all members encapsulatedin the sealed container.

With this structure, incorporation of contaminants in the sealedcontainer is further reliably prevented during device production.

The method for producing a nitride semiconductor laser light sourceaccording to the second aspect of the present invention may furthercomprise a step of, before the ashing step, heating the surface of thelaser chip, the stem, or the cap to 200° C. or higher and 350° C. orlower, or a step of, after the ashing step and before the capping step,heating the surface of the laser chip, the stem, or the cap to 200° C.or higher and 350° C. or lower.

As described in relation to the production method according to the firstaspect, since gases containing contaminants such as hydrocarboncompounds and siloxane are decomposed and evaporated when heated to 200°C. or higher, with the above structures, the contaminants are removedcompletely off the surfaces of the main constituent members. It shouldbe noted, however, that when the treatment temperature exceeds 350° C.,there is a high risk of the solder that joints the constituent membersbeing melted by heat and thereby the laser light source being broken. Itis therefore preferable to make the heating temperature 350° C. orlower.

(4) An apparatus for producing a nitride semiconductor laser lightsource which realizes the method for producing a nitride semiconductorlaser light source according to the second aspect of the presentinvention is configure as follows.

An apparatus for producing a nitride semiconductor laser light sourcecomprises: an ashing treatment equipment for cleaning surfaces of anitride semiconductor laser chip, a stem for mounting the laser chipthereon, and a cap for covering the laser chip, the treatment equipmentexposing the surfaces with an excited oxygen atom; and a capping portionfor supplying a first inert gas onto the cleaned surfaces of the laserchip, the stem, and the cap, and for encapsulating the laser chip in asealed container composed of the stem and the cap in an atmosphere ofthe first inert gas.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross section showing an example of the nitridesemiconductor laser light source produced by a production methodaccording to the present invention.

FIG. 2 is a schematic view showing an outline of the structure of anapparatus for producing the laser light source according to a firstaspect of the present invention.

FIG. 3 is a schematic view showing in greater detail the structure ofthe apparatus for producing the laser light source shown in FIG. 2.

FIG. 4 is a schematic cross section showing an example of a nitridesemiconductor laser light source of the prior art.

FIG. 5 is a schematic cross section of a nitride semiconductor laserlight source in which the laser light emission facet has deteriorated(contamination).

FIG. 6 is a schematic view showing an apparatus for producing a laserlight source according to a second aspect of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention will be described by reference to preferredembodiments.

Embodiment 1-1

FIG. 1 is a schematic cross section showing an outline of the structureof a nitride semiconductor laser light source produced by a method ofproducing a nitride semiconductor laser light source according to afirst aspect of the present invention. As shown in FIG. 1, nitridesemiconductor laser light source 17 has nitride semiconductor laser chip15 with a light emission wavelength of 420 nm or shorter, stem 10 formounting laser chip 15 thereon, and bell-shaped cap 13. Nitridesemiconductor laser light source 17 is formed by encapsulating laserchip 15 in a sealed container that is in turn formed by adhering cap 13to stem 10. This embodiment describes an example in which an inert gasis used both for a first atmosphere and a second atmosphere.Accordingly, the sealed container is filled with an inert gas (nitrogengas or helium gas).

The term nitride semiconductor laser chip is intended to mean a nitridesemiconductor laser device or a nitride semiconductor super luminescentdiode.

Bell-shaped cap 13 has, in a top portion, window portion 14, and throughwindow portion 14, the forward emission laser light of laser chip 15 isemitted outside the light source. On stem 10 is provided light detectingelement 16 by which the emission amount of the backward emission laserlight of laser chip 15 is detected, so that the emission amount of thelaser light is kept uniform by adjusting the driving voltage of thelaser chip in a feedback manner.

Laser chip 15 is supported by chip-equipped portion 11 extended fromstem 10. This nitride semiconductor laser chip can be mounted on thestem while fixed to a sub-mount. Through stem 10, electrode lead wires12 are provided. Electrode lead wires 12 are conducted to laser chip 15and light detecting element 16 such as a photo diode via a connectingwire (not shown).

Nitride semiconductor laser light source 17 was prepared in thefollowing manner.

First, constituent members of nitride semiconductor laser light source17 were prepared including: stem 10 made of iron and coated with, forexample, gold on the surface, with electrode lead wires 12 made of, forexample, gold wires penetrating through the principal surface of stem10; nitride semiconductor laser chip 15 prepared in a known method andhaving a resonator facet and a light emission wavelength of 420 nm orshorter; bell-shaped cap 13 made of metal and having on its top portionwindow portion 14 that is made of glass and allows laser light totransmit therethrough; light detecting element 16 such as a photo diode;and a connecting wire. The stem may be such that in order to enhance theradiation of heat generated at the chip during operation, copper, whichhas high heat conductivity, is provided at the portion of stem 10 wherelaser chip 15 is directly mounted.

The above-described constituent members of the laser light source wereplaced in baking furnace 22 in an apparatus for producing a laser lightsource as shown in the outline view of FIG. 2, and then, as describedlater, the surface of each constituent member was subject to cleaningtreatment (baking step). The apparatus for producing a laser lightsource mainly had main portion 20 housing capping portion 21 and bakingfurnace 22, and carry-in portion 23 and carry-out portion 24, eachprovided adjacent to main portion 20.

The structure of the apparatus for producing a laser light source willbe described in greater detail. As shown in FIG. 3, provided in mainportion 30 having capping portion 31 and baking furnace 32 are inert gasentry port 36 through which inert gas 35 is supplied into the mainportion, and inner-main-portion atmosphere exhaust port 37 through whichthe atmosphere inside the main portion is exhausted outside. In thepassage of inert-gas entry port 36, impurity-removing filter 38 isprovided by which impurities in inert gas 35 are removed prior to supplythereof into the main portion.

Adjacent to main portion 30, carry-in portion 33 is provided on one sideof main portion 30 and carry-out portion 34 is provided on the otherside of main portion 30. Carry-in portion 33 has door 33 b forcontrolling conduction and separation between the carry-in portion andthe main portion by opening and closing movement. Carry-out portion 34has door 34 b for controlling conduction and separation between thecarry-out portion and the main portion. Further, carry-in portion 33 hasdoor 33 a for controlling conduction and separation between the outsideand the carry-in portion, and carry-out portion 34 has door 34 a forcontrolling conduction and separation between the outside and thecarry-out portion.

In addition, carry-in portion 33 has inert-gas entry port 33 c throughwhich inert gas 35 is supplied into the carry-in portion, andinner-carry-in-portion atmosphere exhaust port 33 d through which theatmosphere inside the carry-in portion is exhausted outside. Carry-outportion 34 has inert-gas entry port 34 c through which inert gas 35 issupplied into the carry-out portion, and inner-carry-out-portionatmosphere exhaust port 34 d through which the atmosphere inside thecarry-out portion is exhausted outside. On each passage of inert-gasentry ports 33 c and 34 c, impurity removing filter 38 is provided bywhich impurities in inert gas 35 are removed.

The cleaning treatment will be described below. As described above, thecleaning treatment by baking is intended to mean that by heating thesurface of the target object, contaminants adhered on the surface suchas siloxane, organic compounds and moisture are decomposed and removedin the form of gas.

First, the constituent members of the laser light source includingnitride semiconductor laser chip 15 with a light emission wavelength of420 nm or shorter, stem 10 with laser chip 15 mounted thereon, and cap13 were carried into carry-in portion 33 through door 33 a. Then, in asealed state with door 33 a and door 33 b being closed, inert gas 35 wassupplied through inert-gas entry port 33 c, and the ambient atmospherecomponents inside the carry-in portion were exhausted outside throughexhaust port 33 d, so that the carry-in portion was filled with inertgas 35.

Simultaneously, into main portion 30 in a sealed state with door 33 band door 34 b being closed, inert gas 35 was supplied through inert-gasentry port 36, and the ambient atmosphere components inside the mainportion were exhausted outside through exhaust port 37, so that the mainportion was filled with inert gas 35.

Next, door 33 b, which was between carry-in portion 33 and main portion30, was opened to move the constituent members of the laser light sourcefrom the carry-in portion to the baking furnace 32. Then, in an inertgas, each constituent member was heated at 300° C. for 24 hours todecompose and remove the contaminants adhered on the surface of eachconstituent member in the form of gas, thus cleaning each surface(baking step). During the baking step, fresh inert gas is continuouslysupplied into the main portion, and the atmosphere containing gasifiedcontaminants is exhausted immediately outside the main portion. Thescattered contaminants therefore do not re-adhere to the surfaces of themembers in the main portion.

The baking temperature at the time of the baking can be selectedarbitrarily from the range from 100° C. to 500° C. A reason for thisrange is that if the treatment temperature is lower than 100° C.,organic compounds and siloxane are not sufficiently decomposed andevaporated, making it impossible to clean the constituent members of thelaser light source. On the other hand, if the treatment temperatureexceeds 500° C., heat damage occurs on the nitride semiconductor laserchip, and the cap and stem are deformed by heat. In the case where thetreatment temperature exceeds 350° C., there is a high risk of thesolder that joints the constituent members being melted by heat andthereby the laser light source being broken. It is therefore furtherpreferable to set the heating temperature in the baking step at 100° C.to 350° C.

Although the baking time can be selected arbitrarily from the rangebetween 10 minutes and 24 hours, adjustment needs to be carried outconsidering the trade-off between the treatment temperature and thetreatment time, examples including setting the time at 10 minutes whenthe temperature is 500° C., 30 minutes for a temperature of 350° C., 2hours for a temperature of 200° C., and 24 hours for a temperature of100° C.

As the inert gas, it is preferable to use helium gas and nitrogen gas,as described above. A reason for this is that helium gas has very highheat conductivity, and by using helium gas as a heat radiation mediumheat damage during operation of the nitride semiconductor laser chip issignificantly reduced. Another reason is that because nitrogen gas ischeaper than other, inert gases, the use of nitrogen gas for the inertgas reduces the production cost of the laser light source.

Even if only one of the laser chip, stem, and cap is subject to thecleaning treatment in the baking step, intrusion of contaminants intothe sealed container at the time of device production can be preventedto some extent. However, to significantly prevent contaminants fromintruding into the laser light source, it is preferable to subject thelaser chip, stem, and chip collectively to the cleaning treatment, andit is more preferable to clean the surfaces of all the members to beencapsulated in the sealed container. In the case of mounting the laserchip on the stem by fixing the laser chip to a sub-mount, it is ofcourse preferable to clean the sub-mount.

The constituent members of the laser light source having respectivesurfaces subject to the cleaning treatment in the baking step were movedto capping portion 22, and in an inert gas, bell-shape cap 13 and stem10 were adhered and sealed with inert gas while housing nitridesemiconductor laser chip 15 inside cap 13, thus constructing nitridesemiconductor laser light source 17 as shown in FIG. 1 (capping step).

Subjecting the stem with the laser chip mounted thereon in advance tothe cleaning treatment is preferable in that it is not necessary tomount the laser chip on the stem in the capping step, so that theencapsulation of the laser chip in the sealed container is simplified.

In the capping step, adjusting the pressure of the inert gas inside themain portion to ambient atmosphere pressure (760×133.322 Pa (760 Torr))or lower is preferable in that the pressure of the encapsulation gasinside the sealed container becomes that of the ambient atmosphere orlower, so that the adhesivity of the cap after sealing is enhanced.

Next, door 34 b, which was between main portion 30 and carry-out portion34, was opened to move the constructed laser light source to the insideof carry-out portion 34. Lastly, in a sealed state with door 34 b anddoor 34 a being closed, inert gas 35 was supplied through inert-gasentry port 34 c. Then, after the pressure inside the carry-out portionwas adjusted to be equivalent to that of the ambient atmosphere, door 34a was opened and the laser light source was taken out of the carry-outportion.

Using nitride semiconductor laser light source 17 thus prepared, along-term aging test, in which a laser is continuously driven, wascarried out. To carry out the aging test in an accelerated manner, thetreatment temperature was set at 60° C. or higher. When the laser wascontinuously driven at a light output of 30 mW, it has been observedthat the laser continued providing light emission at a constant outputeven after more than 3000 hours of drive, and that the facet of theresonator of the laser chip had not deteriorated, which is a main causeof the deterioration with time of laser characteristics. On the otherhand, a conventional laser light source could not be driven for 3000hours under the same driving conditions.

The conventional laser light source was disassembled to examine thelaser chip. As shown in FIG. 5, this laser chip had substrate 100,nitride semiconductor layer 101 formed on substrate 100, active layer102 formed on semiconductor layer 101, nitride semiconductor layer 103formed on active layer 102, insulation layer 104 formed on semiconductorlayer 103, positive electrode 105, and negative electrode 106. It wasobserved that the resonator facet in the vicinity of active layer 102 ofthe laser chip had deterioration (contamination) 110.

As a result of a study carried out by the present inventors, it isconsidered that in a conventional laser light source with zeoliteadsorbent, the heat generated during continuous driving causes part ofonce adsorbed hydrocarbon compounds and siloxane to float off thezeolite adsorbent in the encapsulated atmosphere, and that somecontaminants are adhered to the laser facet before adsorbed by thezeolite adsorbent. Thus, an increase in lifetime is inhibited.

In the method for producing the laser light source according toembodiment 1-1, by carrying out the baking step prior to the cappingstep, in which the laser chip is encapsulated in the sealed containercomposed of the stem and cap, contaminants are removed away from theinside of the sealed container and the surface of the laser chip. Sincethis significantly reduces the amount of contaminants contained in thesealed container at the time of the capping, a long-life type nitridesemiconductor laser, light source as described above is obtained.

Also in the method for producing the laser light source according toembodiment 1-1, during the time between the baking step and completionof the capping step, the constituent members of the laser light sourceare not exposed to the ambient atmosphere but kept in inert gas in asealed state. The contaminants are therefore not re-adhered to thecleaned surfaces of the members. Thus, contaminants are reliablyprevented from being incorporated in the sealed container at the time ofdevice production.

As the supplied inert gas (second atmosphere) in the capping step, it ispossible to use an inert gas of a kind different from the inert gas(first atmosphere) supplied at the time of the baking step. However, itis preferred to use the same kind of inert gas throughout the productionprocess of the laser light source in that work associated with supply ofgas is simplified, and that the laser light source is produced cheaplycompared with the use of a plurality of different kinds of gases.

In addition, inert gas 35 to be supplied is not limited to theabove-described helium gas and nitrogen gas.

As has been described hereinbefore, when contaminants are incorporatedinside the laser light source, the facet of the resonator of the laserchip tends to deteriorate remarkably as the light emission wavelength ofthe laser light source becomes shorter. However, with the method forproducing the laser light source according to embodiment 1-1, whileusing a laser chip of a very short wavelength of 420 nm or shorter,which is a light emission wavelength in the blue-to-ultraviolet regions,since the amount of contaminants incorporated inside the sealedcontainer at the time of production is significantly reduced, thelong-time operation of, the laser light source is enabled.

Oxygen gas may be added in the second atmosphere, which is anencapsulation gas for use in encapsulating the laser chip in the sealedcontainer composed of the stem and cap. Addition of oxygen gasstabilizes laser chip characteristics such as electrical characteristicswhen the laser light source is operated for a long period of time. Theoxygen gas concentration of the second atmosphere is preferably 100 ppmor higher and 80% or lower, more preferably from 0.1% to 40%, and mostpreferably from 1% to 18%. If the oxygen concentration is too low, theeffect of characteristics stabilization is not sufficiently obtained. Ifthe oxygen concentration is too high, the oxygen gas is feared todeteriorate laser chip characteristics.

The encapsulation gas preferably has low moisture concentration in thatwith high moisture concentration the moisture in the encapsulatedatmosphere causes a tendency of laser chip characteristics to easilydeteriorate. Specifically, the moisture concentration is preferably 1000ppm or lower, more preferably 400 ppm or lower, and most preferably 100ppm or lower. This range is because by using an inert gas with moistureconcentration in the above range, the amount of the H₂O present in thesealed container is reduced, so that the facet of the resonator isprevented from deteriorating, which is considered to result frommoisture ionized by exposure of laser light of short wavelength.

With the above considerations combined, the second atmosphere preferablycontains nitrogen gas or helium gas as an inert gas, has oxygen gasmixed at the above ratio, and has moisture concentration in the aboverange.

When, instead of using the inert gas (first atmosphere) supplied at thetime of the baking step and the inert gas (second atmosphere) suppliedat the time of the capping step, dry air with a moisture concentrationof 1000 ppm or lower was used, the same advantageous effects wereobtained. It is considered that this is because dry air with a moistureconcentration of 1000 ppm or lower is mainly made of an inert gas(approximately 78% nitrogen gas and approximately 1% argon gas) andapproximately 21% oxygen gas. In this case, the production cost isreduced compared with the above embodiment, in which an inert gas or amixture gas of oxygen gas and inert gas is used.

Embodiment 1-2

Embodiment 1-2 according to the first aspect of the present invention isthe same as embodiment 1-1 except that the insides of carry-in portion33, in which the constituent members of the laser light source are keptimmediately before moved to main portion 30, and main portion 30 are ina vacuum state (i.e., the first atmosphere and second atmosphere areturned into a vacuum). Accordingly, descriptions also applicable toembodiment 1-1 will not be elaborated upon here. It is noted that theterm vacuum is intended to mean an atmosphere of an atmospheric pressureof 1×133.322 Pa (1 Torr) or lower. It is also noted that the sealedcontainer of the resulting laser light source has a vacuum.

The vacuation of the inside of carry-in portion 33 was carried out suchthat after the constituent members of the laser light source were placedin carry-in portion 33 through door 33 a, the ambient atmospherecomponents in the carry-in portion were exhausted outside in a sealedstate with door 33 a and door 33 b being closed. Simultaneously, in asealed state with door 33 b and door 34 b being closed, the ambientatmosphere components in the main portion were exhausted outside throughexhaust port 39, thus vacuating the inside of main portion 30.

In the nitride semiconductor laser light source according to embodiment1-2, the amount of contaminants incorporated in the sealed container atthe time of production is significantly reduced, similarly to embodiment1-1. Therefore, while using a laser chip of a very short wavelength of420 nm or shorter, which is a light emission wavelength in theultraviolet region, the long-time operation of the laser light source isenabled. Further, since the sealed container has a vacuum, theadhesivity of the cap after sealing is significantly increased.

Embodiment 2

Next, an embodiment according to a second aspect of the presentinvention will be described. A nitride semiconductor laser light sourceproduced by the method for producing a nitride semiconductor laser lightsource according to embodiment 2 is the same as the nitridesemiconductor laser light source in embodiment 1-1 except that the lightemission wavelength of nitride semiconductor laser chip 15 is 450 nm orshorter, as shown in the schematic view of FIG. 1. Accordingly,descriptions on the members of the nitride semiconductor laser lightsource will not be provided. This embodiment describes an example inwhich only an inert gas is used for a first gas.

Method for Producing a Laser Light Source

First, constituent members of nitride semiconductor laser light source17 were prepared including: stem 10 made of iron and coated with, forexample, gold on the surface, with electrode lead wires 12 made of, forexample, gold wires penetrating through the principal surface of stem10; nitride semiconductor laser chip 15 prepared in a known method andhaving a resonator facet and a light emission wavelength of 450 nm orshorter, bell-shaped cap 13 made of metal and having on its top portionwindow portion 14 that is made of glass and allows laser light totransmit therethrough; light detecting element 16 such as a photo diode;and a connecting wire. The stem may be such that in order to enhance theradiation of heat generated at the chip during operation, copper, whichhas high heat conductivity, is provided at the portion of stem 10 wherelaser chip 15 is directly mounted.

The above-described constituent members of the laser light source wereplaced in ashing treatment equipment 121 of apparatus 120 for producinga laser light source as shown in the outline view of FIG. 6. Then, asdescribed later, the surface of each constituent member was subject tocleaning treatment (ashing step).

The cleaning treatment will be described. As described above, thecleaning treatment is intended to mean that by exposing the surface ofthe target object with an excited oxygen atom, the contaminants adheredon the surface such as siloxane, organic compounds, and moisture areoxidized and removed in the form of gas.

First, the atmosphere inside ashing treatment equipment 121 havingplaced therein the constituent members of the laser light source wasadjusted to an oxygen concentration of 100%, ambient atmosphere pressure(760×133.322 Pa), and 200° C.

Next, under this atmosphere, the surface of each constituent member ofthe laser light source was irradiated with ultraviolet light from alow-pressure mercury lamp, thus subjecting the surface of each member tocleaning treatment. The ultraviolet light had its peak of wavelength inthe range 184.9 nm to 253.7 nm. The distance between the sample and thelamp was set at approximately 2 to 10 nm, the radiation intensity wasset at approximately 5 to 10 mW/cm², and the radiation time was set at 1minute to 20 hours.

The cleaning treatment will be described in greater detail. Whenultraviolet light under the above radiation conditions is radiated tooxygen gas (O₂), the oxygen gas is decomposed and an excited oxygen atom(O (1D)) is generated. Because an excited oxygen, atom (O (1D)) hasstrong oxidization force, when the surface of each constituent member ofthe laser light source is exposed to the excited oxygen atom,contaminants adhered to the surface of each member such as siloxane andorganic compounds are oxidized and decomposed to be gasified, andscattered off the surface of each constituent member in the atmosphereof the ashing treatment equipment. In the ashing treatment equipment,ventilation for a new atmosphere is carried out continuously, and theatmosphere containing gasified contaminants is exhausted immediatelyoutside the ashing treatment equipment. The scattered contaminantstherefore do not re-adhere to the surfaces of the members in the ashingtreatment equipment.

In the cleaning treatment according to the present invention, it isimportant to expose the surfaces of the members with highly reactive gassuch as the above-described excited oxygen atom. In view of this, otherembodiments than the above are possible; for example, the surfaces ofthe members can be exposed with ozone (O₃) generated by using a knownozone-gas generating method or with an excited oxygen atom generated inadvance in such a manner that oxygen gas or ozone gas is exposed withultraviolet light. In this case, irradiating the surfaces of the memberswith ultraviolet light while exposing the surfaces with ozone and anexcited oxygen atom is preferable in that the reactivity of the ozoneand excited oxygen atom is further enhanced.

The treatment temperature inside the ashing treatment equipment duringthe cleaning treatment is preferably from 100° C. to 500° C., and morepreferably from 200° C. to 350° C. A reason for this range is that inaddition to an accelerated increase in the oxidization activity of theexcited oxygen atom and the like upon increase in the treatmenttemperature, when the treatment temperature is made 200° C. or higher,the cleaning treatment on the surface of each constituent member of thelaser light source is promoted by the baking effect of decomposing andevaporating the organic compounds and siloxane. Another reason is thatby making the treatment temperature 100° C. or higher, moisture isevaporated off the surface of each member. On the other hand, exceeding500° C. is not preferable in that heat damage occurs on the nitridesemiconductor laser chip, and the cap and stem are deformed by heat. Inthe case where the treatment temperature exceeds 350° C. there is a highrisk of the solder that joints the constituent members being melted byheat and thereby the laser light source being broken.

Insofar as the excited oxygen atom and ozone gas exhibit a sufficienteffect of decomposing contaminants, the ashing treatment equipmentduring the cleaning treatment may contain an inert gas (second gas),composed of nitrogen gas, helium gas, and the like, other than oxygengas, ozone gas, and excited oxygen atom. Specifically, such anembodiment is possible that a gas in which an inert gas and oxygen gasare mixed together at an oxygen concentration of 5% to 100% is suppliedto an ozone-gas generating device attached to the ashing treatmentequipment. Because helium gas has high heat conductivity, by usinghelium gas as a heat radiation medium, heat damage during operation ofthe nitride semiconductor laser chip is significantly reduced. On theother hand, because nitrogen gas is cheaper than other inert gases, theuse of nitrogen gas for the inert gas reduces the production cost of thelaser light source.

The time for the cleaning treatment is preferably from 1 minute to 20hours, as described above. This is because if the treatment time isshorter than 1 minute, contaminants cannot be sufficiently decomposed.On the other hand, the upper limit for the treatment time is notspecified. However, because the degree of cleaning becomes practicallysufficient after 20 hours of cleaning, the treatment time is preferablyin the above range.

Even if only one of the laser chip, stem, and cap is subject to thecleaning treatment in the ashing step, intrusion of contaminants intothe sealed container at the time of device production can be preventedto some extent. However, to significantly prevent contaminants fromintruding into the laser light source, it is preferable to subject thelaser chip, stem, and chip collectively to the cleaning treatment, andit is more preferable to clean the surfaces of all the members to beencapsulated in the sealed container. In the case of mounting the laserchip on the stem by fixing the laser chip to a sub-mount, it is ofcourse preferable to clean the sub-mount.

Next, the steps after the treatment step will be described. In apparatus120 for producing a laser light source used in this embodiment, ashingtreatment equipment 121 and capping portion 122, in which encapsulationof the laser chip in the sealed container composed of the stem and capis carried out, are independent, and ashing treatment equipment 121 andcapping portion 122 are connected together by pass box portion 123 in ahermetic state.

After completion of the cleaning treatment, supply of the excited oxygenatom, ozone, or oxygen gas into the ashing treatment equipment wasdiscontinued. At the same time, an inert gas composed of nitrogen gas,helium gas, and the like was supplied, so that the surface of eachconstituent member of the laser light source in the ashing treatmentequipment was exposed only with the inert gas. An inert gas was suppliedto the insides of pass box portion 123 and capping portion 122 at apressure higher than 760×133.322 Pa, thus making atmosphere gas.

Next, the cleaned constituent members of the laser light source weremoved from ashing treatment equipment 121 past pass box portion 123 intocapping portion 122. As described above, since ashing treatmentequipment 121 and capping portion 122 are connected togetherhermetically by pass box portion 123, and an inert gas is filled in eachportion, the surfaces of the constituent members are not exposed to theambient atmosphere during the movement. Thus, during the cleaningtreatment and the capping step described later, contaminants do notre-adhere to the surfaces of the constituent members.

Lastly, in capping portion 122, bell-shape cap 13 and stem 10 wereadhered and sealed with inert gas while housing nitride semiconductorlaser chip 15 inside cap 13, thus constructing nitride semiconductorlaser light source 17 as shown in FIG. 1 (capping step).

Subjecting the stem with the laser chip mounted thereon in advance tothe cleaning treatment is preferable in that it is not necessary tomount the laser chip on the stem in the capping step, so that theencapsulation of the laser chip in the sealed container is simplified.

Using this nitride semiconductor laser light source, a long-term agingtest, in which a laser is continuously driven, was carried out. To carryout the aging test in an accelerated manner, the treatment temperaturewas set at 60° C. or higher. When the laser was continuously driven at alight output of 30 mW, it has been observed that the laser continuedproviding light emission at a constant output even after more than 3000hours of drive, and that the facet of the resonator of the laser chiphad not deteriorated, which is a main cause of the deterioration withtime of laser characteristics. On the other hand, a conventional laserlight source could not be driven for 3000 hours under the same drivingconditions, and as shown in FIG. 5, deterioration (contamination) 110was observed on the facet of the resonator of the laser chip.

A reason for the results is considered to be the same as that studied inembodiment 1-1.

In the method for producing the laser light source according to thisembodiment, by carrying out the ashing step prior to the capping step,in which the laser chip is encapsulated in the sealed container composedof the stem and cap, contaminants are removed away from the inside ofthe sealed container and the surface of the laser chip. Since thissignificantly reduces the amount of contaminants contained in the sealedcontainer at the time of the capping, a nitride semiconductor laserlight source with long-life characteristics as described above isobtained.

Also in the method for producing the laser light source according tothis embodiment, during the time between the ashing step and completionof the capping step, the constituent members of the laser light sourceare not exposed to the ambient atmosphere but kept in inert gas in ahermetic state. The contaminants therefore do not re-adhere to thecleaned surfaces of the members. Thus, contaminants are reliablyprevented from being incorporated in the sealed container at the time ofdevice production, enabling the further long-time operation of the laserlight source.

By filling capping portion 122 with the inert gas at a pressure of760×133.322 Pa (760 Torr) or higher, the pressure inside the sealedcontainer is adjusted to be higher than the ambient atmosphere pressure.This prevents the ambient atmosphere from flowing into the completedsealed container, that is, contaminants are prevented from intrudinginto the sealed container. Thus, the long-time operation of the laserlight source is enabled.

Insofar as contaminants are prevented from intruding into the sealedcontainer at the time of production of the laser light source, theapparatus for producing the laser light source is not limited toabove-described production apparatus 120, in which ashing treatmentequipment 121 and capping portion 122 are connected togetherhermetically by pass box portion 123. For example, such a productionapparatus of integral structure may be used that acts both as the ashingtreatment equipment and the capping portion without the pass boxportion.

As the inert gas supplied after the cleaning treatment, it is possibleto use an inert gas of a kind different from the inert gas supplied atthe time of the ashing. However, it is preferred to use the same kind ofinert gas throughout the production process of the laser light source inthat work associated with supply of gas is simplified, and that thelaser light source is produced cheaply compared with the use of aplurality of different kinds of inert gases.

Since gases containing contaminants such as hydrocarbon compounds andsiloxane are decomposed and evaporated when heated to 200° C. or higher,in order to completely remove the contaminants, it is preferable to heatthe laser light source or its constituent members to 200° C. or higher,before the ashing step, or after the ashing step and before the cappingstep. To prevent the solder that joints the constituent members frombeing melted by heat and causing the laser light source to be broken, itis preferable to set the heating temperature at 350° C. or lower.

When contaminants are incorporated inside the laser light source, thefacet of the resonator of the laser chip tends to deteriorate remarkablyas the light emission wavelength of the laser light source becomesshorter. However, in this embodiment, while using a laser chip of a veryshort wavelength of 450 nm or shorter, and further, 420 nm or shorter,which are light emission wavelengths in the blue-to-ultraviolet regions,the long-time operation of the laser light source is enabled.

As in embodiment 1-1, oxygen gas may be added in the encapsulation gas,which is used in encapsulating the laser chip in the sealed containercomposed of the stem and cap.

The encapsulation gas preferably has low moisture concentration in thatwith high moisture concentration the moisture in the encapsulatedatmosphere causes a tendency of laser chip characteristics to easilydeteriorate.

The advantageous effects of addition of oxygen gas and its preferableconcentration, and preferable moisture concentration are the same asthose in embodiment 1-1.

When, instead of using the inert gas (first atmosphere) supplied at thetime of the ashing step and the inert gas (second atmosphere) suppliedat the time of the capping step, dry air with a moisture concentrationof 1000 ppm or lower was used, the same advantageous effects wereobtained. The reason for this is considered to be the same as thatstudied in embodiment 1-1. In the case of using dry air with a moistureconcentration of 1000 ppm or lower, the production cost is reducedcompared with the case of using an inert gas or a mixture gas of oxygengas and inert gas.

In this case, dry air in which impurities such as contaminants areremoved by a filter or the like is preferably used. Even whencontaminants are contained in the dry air, by making the moistureconcentration 1000 ppm or lower, more preferably 400 ppm or lower, andmost preferably 100 ppm or lower, the deterioration (contamination) ofthe facet is inhibited.

As has been described hereinbefore, according to the present invention,since contaminants do not easily intrude into the laser light sourceduring production, the present invention finds applications also inpreventing the facet of the resonator of the laser chip fromdeteriorating. Thus, the present invention, while using a laser chip ofa short wavelength of 450 nm or shorter, and further, 420 nm or shorter,which are light emission wavelengths in the blue-to-ultraviolet regions,enables the long-time operation of the laser light source.

1. A method for producing a nitride semiconductor laser light source,the nitride semiconductor laser light source comprising a nitridesemiconductor laser chip, a stem for mounting the laser chip thereon,and a cap for covering the laser chip, the laser chip being encapsulatedin a sealed container composed of the stem and the cap, the methodcomprising the steps of: a baking step of cleaning a surface of thelaser chip, the stem, and the cap, the baking step comprising heatingthe laser chip, the stem, and the cap in a first atmosphere so as toremove contaminants from the nitride semiconductor laser light source inthe form of a gas; and a capping step of, after the baking step,encapsulating the laser chip in the sealed container composed of thestem and the cap, the capping step being carried out in a secondatmosphere.
 2. The method for producing a nitride semiconductor laserlight source according to claim 1, wherein the first atmosphere and thesecond atmosphere each have a vacuum.
 3. The method for producing anitride semiconductor laser light source according to claim 1, wherein:the first atmosphere comprises only an inert gas; and the secondatmosphere comprises an inert gas of a kind identical to or differentfrom the inert gas of the first atmosphere.
 4. The method for producinga nitride semiconductor laser light source according to claim 3, whereinthe first atmosphere and the second atmosphere are identicalatmospheres.
 5. The method for producing a nitride semiconductor laserlight source according to claim 3, wherein each of the inert gases isnitrogen gas or helium gas.
 6. The method for producing a nitridesemiconductor laser light source according to claim 3, wherein apressure of the second atmosphere is 760×133.322 Pa or lower.
 7. Themethod for producing a nitride semiconductor laser light sourceaccording to claim 1, wherein: the first atmosphere comprises an inertgas, or an inert gas and oxygen gas; and the second atmosphere comprisesan inert gas and oxygen gas.
 8. The method for producing a nitridesemiconductor laser light source according to claim 7, wherein the firstatmosphere and the second atmosphere are identical atmospheres.
 9. Themethod for producing a nitride semiconductor laser light sourceaccording to claim 7, wherein each of the inert gases is nitrogen gas orhelium gas.
 10. The method for producing a nitride semiconductor laserlight source according to claim 7, wherein a pressure of the secondatmosphere is 760×133.322 Pa or lower.
 11. The method for producing anitride semiconductor laser light source according to claim 1, whereinthe first atmosphere and the second atmosphere each have dry air with amoisture concentration of 1000 ppm or lower.
 12. The method forproducing a nitride semiconductor laser light source according to claim11, wherein the first atmosphere and the second atmosphere are identicalatmospheres.
 13. The method for producing a nitride semiconductor laserlight source according to claim 1, wherein the nitride semiconductorlaser chip has a light emission wavelength of 420 nm or shorter.
 14. Themethod for producing a nitride semiconductor laser light sourceaccording to claim 1, wherein the baking step comprises heating thelaser chip, the stem, or the cap to 100° C. or higher and 500° C. orlower.
 15. The method for producing a nitride semiconductor laser lightsource according to claim 1, wherein a treatment temperature during thebaking step is from 200° C. to 350° C.
 16. The method for producing anitride semiconductor laser light source according to claim 1, whereinthe baking step comprises heating the laser chip, the stem, or the capfor 10 minutes or longer and 24 hours or shorter.
 17. The method forproducing a nitride semiconductor laser light source according to claim1, wherein the baking step comprises heating the laser chip, the stem,or the cap for 30 minutes or longer and 2 hours or shorter.
 18. Themethod for producing a nitride semiconductor laser light sourceaccording to claim 1, wherein a gas constituting the first atmosphere iscontinuously supplied in the baking step.